R5972D datasheet(22/35 Pages) STMICROELECTRONICS

Part #	R5972D

Description	Up to 1.5 A step-down switching regulator for aerospace applications

PDF	35 Pages

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Manufacturer	STMICROELECTRONICS [STMicroelectronics]

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22 / 35 page

Application information

R5972D

22/35

DocID026873 Rev 1

compensate for the losses in the overall application. For this reason, the switching losses

related to the RDSON increase compared to an ideal case.



Switching losses due to turning ON and OFF. These are derived using the following

equation:

Equation 23

Where TRISE and TFALL represent the switching times of the power element that cause the

switching losses when driving an inductive load (see Figure 12). TSW is the equivalent

switching time.

Figure 12. Switching losses



Quiescent current losses.

Equation 24

Where IQ is the quiescent current.

Example 2



VIN = 12 V



VOUT = 3.3 V



IOUT = 1.5 A

RDS(on) has a typical value of 0.25 at 25 °C and increases up to a maximum value of 0.5. at

150 °C. We can consider a value of 0.4

.

TSW is approximately 70 ns.

IQ has a typical value of 2.5 mA at VIN = 12 V.

PSW

VIN IOUT

TON TOFF



------------------------------------



FSW VIN



IOUT TSW



FSW



VIN IQ



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